Primary olfactory neuropils in both vertebrates and invertebrates are characterized by arrays of synaptic glomeruli, each of which processes information about particular attributes of odorous stimuli; but little is known about how these striking spatial arrays develop. In the moth Manduca sexta, the olfactory neuropil comprises 64 glomeruli that appear to be similar in males and females, and two to three specialized and easily recognizable glomeruli that are unique to each sex and that process information about odors important for reproduction. Previous experiments have demonstrated that male-specific group of specialized glomeruli, including recruitment of female target neurons into that circuitry. Furthermore, even if entering the brain from an abnormal position, those male-specific axons find the correct target site. Thus, the sexually dimorphic olfactory system of Manduca offers a special opportunity to investigate a central question in olfactory development: what cellular interactions underlie the development of the array of glomeruli. The proposed project addresses the question, with two specific aims: (1) to explore aspects of the "address" that male-specific olfactory receptor axons recognize in the target olfactory neuropil and to determine whether synaptic interactions between those axons and particular target neurons underlie the dendritic morphology that the axons induce in those neurons; and (2) to determine the role of nitric oxide, a gaseous intercellular signaling molecule which appears to be released by developing olfactory axons, in the development of both sexually isomorphic and sexually dimorphic glomeruli in the antennal lobe. The project, taking advantage of the relative cellular simplicity of the moth olfactory system, and using state-of-the-art microscopical methods in addition to electrophysiological, biochemical, and molecular biological approaches is expected to provide insights into the development of less accessible mammalian olfactory systems.